Let the germination probability (the probability that a seed sprouts) for seed A be Pa and B be Pb.
a) You plant two seeds of the same kind. If you turn heads or tails of what sort you plantet, what is the probability that 2 seeds germinate?
b) A student plant 2 seeds, but he had forgotten to note what sort of seed he had planted. What is the probability that it was A if both germinate?